Strut mount

ABSTRACT

The present invention provides a strut mount comprising an inner member ( 12 ) to which an upper extremity of a rod of a buffer is fixed, an outer member ( 14 ) attached to a vehicle while surrounding an outer circumference of the inner member, and an elastomer ( 16 ) interposed between both members to dampen vibration, wherein an attachment piece ( 28 ) of an outer fitting ( 14 ) and an attachment plate ( 2 ) of the vehicle body are curved in the form of a sphere to raise rigidity and improve vehicle running stability. Besides, a non-fastening surface portion ( 36 ) is provided by being lowered via a different level portion ( 34 ) around a bolt fastening surface portion ( 30 ) of the attachment piece ( 28 ), preventing rubber burr from being produced on the fastening surface. Furthermore, by the use of a caulking nut ( 52 ) stuck to the underside of the attachment piece ( 28 ), the weight of the products can be reduced, and cost reduction is accomplished by laborsaving during operations.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/JP01/04091, filed May 16, 2001, whichclaims priority to Japanese Patent Application No. 2000-310055, filedOct. 11, 2000.

FIELD OF THE INVENTION

This invention relates to a strut mount disposed at an attachmentportion of a buffer to a vehicle.

DESCRIPTION OF THE RELATED ART

In general, in a suspension system of an automobile, etc., a so-calledstrut mount is disposed at an attachment portion of a buffer to avehicle body, in order to control vibration, etc. propagated from wheelsto the vehicle body.

FIG. 12 shows an example of a conventional strut mount. The strut mount100 comprises an inner fitting 101 in which the upper extremity of apiston rod 110 of a shock absorber is inserted, an outer fitting 102attached to the vehicle body side, and a rubber elastomer 103 interposedbetween both fittings to dampen input vibration. The rod 110 insertedinto the inner fitting 101 is fixed to the inner fitting 101 when beingfastened by a nut 104. The outer fitting 102 is provided with anattachment piece 105, to which a bolt 107 inserted into a bolt hole 106thereof from below is press fitted and secured. With the bolt 107 liftedup so as to insert into a bolt hole 113 of the vehicle body's attachmentplate 112 from below, by tightening a nut 108 from above the attachmentplate 112 of the vehicle body, the strut mount 100 will be attached tothe vehicle body only by attachment working from above.

Incidentally, it is necessary to secure high rigidity to improve vehiclerunning stability for the attachment plate 112 of the vehicle body, towhich the strut mount 100 is attached. Although the thickness of theattachment plate 112 in the form of a plane has been thickened to securesuch high rigidity so far, securing adequate rigidity is required foreven thin plate thickness, in keeping with weight reduction of thevehicle in recent years.

DISCLOSURE OF THE INVENTION

In view of the aforementioned points, an object of the present inventionis to provide the improvement of vehicle running stability by raisingthe rigidity of the attachment structure of a strut mount to a vehicle.

A strut mount according to a first embodiment of the present inventioncomprises an inner member to which the upper extremity of a rod of abuffer is fixed, an outer member attached to the vehicle whilesurrounding an outer circumference of the inner member, and an elastomerinterposed between the inner and outer members to dampen vibration,wherein the outer member is provided with an attachment piece that isfitted and secured to an attachment plate of the vehicle fromunderneath, the attachment piece being curved in the form of a partialsphere corresponding to the shape of the lower surface of the attachmentplate curved in the form of a partial sphere.

Thus, by curving both the attachment piece of the outer member and theattachment plate of the vehicle body in the form of a sphere, rigiditycan be raised without thickening the attachment plate of the vehiclebody to improve vehicle running stability. Hereupon, the form of asphere denotes a curved surface forming a part of a sphere.

Incidentally, when the attachment piece of the outer member is curved inthe form of a partial sphere, the surface fastening to the vehicle bodyis also in the form of a partial sphere. Accordingly, when a rubberelastomer is formed, it poses a problem that a rubber burr is liable tobe produced when a rubber comes into the fastening surface. Since a boltcannot be tightened by a predetermined torque due to the presence of therubber burr and deteriorated rubber may cause the tightened bolt to beloosened, it is necessary to get rid of the rubber burr after forming,leading to a cause of higher working cost.

Therefore, the present invention provides a strut mount according to asecond embodiment that the elastomer is a rubber elastomer stuck to theinner and outer members by means of die forming, the outer member beingequipped with an attachment piece fitted and secured to an attachmentplate of a vehicle from underneath, the attachment piece being equippedwith a fastening surface portion that is exposed from the rubberelastomer and tightened to the attachment plate of the vehicle by thebolts, and non-fastening surface portion being provided so as to belowered via a different level portion around the fastening surfaceportion.

As for the strut mount, when forming the rubber elastomer, the rubber isprevented from coming into the fastening surface portion by pressing theforcing surface portion provided on the forming die against thenon-fastening surface portion. That is, according to the secondembodiment, since the non-fastening surface portion is provided so as tobe lowered via a different level portion around the fastening surfaceportion of the attachment piece, the non-fastening surface portion canserve as a sealing surface portion to prevent the rubber in a cavity ofthe forming die from getting into the fastening surface, thus preventingthe rubber burr from producing on the fastening surface.

Thus, the second embodiment is to prevent the rubber from coming intothe fastening surface portion by pressing the forcing surface portion ofthe forming die against the non-fastening surface portion. However,since the forcing surface portion is pressed against the non-fasteningsurface, any effect is not produced on fastening to the attachment plateof the vehicle body even if any surface becomes rough due to forcing orurging. Accordingly, a sealing protrusion can be provided on the forcingsurface portion of the forming die and pressed against the non-fasteningsurface portion, thus capable of preventing the rubber more effectivelyfrom coming into the fastening surface. Furthermore, since thenon-fastening surface portion can be configured in the form of a planeas against the spherical fastening surface portion, it is easy for theforming die to press the non-fastening surface portion.

As aforementioned, when both the attachment piece of the outer memberand the attachment plate of the vehicle body are curved in the form of asphere, it is also desired to devise the bolt fastening structure tosecure both the attachment piece and plate. That is, as shown in FIG.11, as for the strut mount in which the bolt 203 is fitted and securedto the attachment piece 202 of the outer fitting 201, when theattachment piece 202 of the outer fitting 201 and the attachment plate210 of the vehicle body are curved in the form of a sphere, each bolt203 fitted and secured to the attachment piece 202 is disposed towardindividual inclined direction as against the direction of movement(perpendicularly) when the strut mount is lifted up. For that purpose,it is necessary to enlarge a bolt hole 211 of the attachment plate 210so that the bolt 203 turned toward the inclined direction can beinserted. However, if the bolt hole 211 is large, it is feared that theproblems in bolt fastening such as looseness may be posed. Therefore, ameans for inserting the bolt without making the bolt hole larger and fortightening the bolt only by operations from above is required.

Accordingly, the present invention is to provide a strut mount accordingto a third embodiment by providing a nut under the attachment piece ofan outer member, screwing a bolt into the nut from above the attachmentplate of the vehicle body, inserting the bolt without making the bolthole larger, and tightening the attachment piece of the outer member tothe underneath of the attachment plate of the vehicle body with a bolt.

When providing the nut for the attachment piece of the outer member, atechnique that a small hole is formed at a prescribed position on theattachment piece, that a burr is formed (burring working) downwardlyaround the circumferential edge of the hole as a cylindrical portion,and that an inner circumferential surface of the cylindrical portion istapped and cut as screw threads to serve as a nut, makes its workingdifficult and complicated. Furthermore, in order to elongate the nut ofa given diameter and cut the required screw threads, it is necessary tothicken the attachment piece, with the result that the weight of thecomponents grows heavier. Besides, as for the method of welding a nut onthe underside of the attachment piece of the outer member, in order toavoid deterioration of rubber elastomer due to welding heat, it isnecessary to weld the nut before working the strut mount or to escapewelding heat by masking around the nut of the attachment piece, wherebymaking the strut mount working difficult and complicated.

Accordingly, the third embodiment adopts a nut caulked and secured onthe lower surface side of the attachment piece. By caulking and securingthe nut in this manner, it is possible to make the thickness of theouter member thinner to reduce the weight of the components, and also toprevent heat that causes the rubber elastomer to be deteriorated,without causing any difficult and complicated working.

A means for caulking and securing the nut is to form a nut attachmenthole on the attachment piece of the outer member and to insert thecaulking nut having a cylindrical portion from underneath the attachmentpiece. When the cylindrical portion is caulked and upset, an outercircumferential surface of the cylindrical portion is stuck fast to aninner circumferential surface of the nut attachment hole, thus capableof sticking the nut on the lower surface side of the attachment piece.

With the cylindrical portion of the caulking nut inserted into the nutattachment hole from the underside, by pressurizing the circumference ofthe nut attachment hole from the direction square to the plate surfaceof the attachment piece to upset the nut attachment hole, the innercircumferential surface of the nut attachment hole is stuck fast to theouter circumferential surface of the cylindrical portion to stick thenut on the lower surface side of the attachment piece.

At this time, provided that the outer circumferential surface of thecylindrical portion of the caulking nut is corrugated, an extra wallsurrounding the nut attachment hole cuts into the corrugated outercircumferential surface of the cylindrical portion as the nut attachmenthole is diminished in diameter, the extra wall acts as a steady rest torestrain the caulking nut from turning together with the bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a strut mount of a first embodiment of thepresent invention and a sectional view taken on line A—A of FIG. 2.

FIG. 2 is a plan view of the strut mount.

FIG. 3 is an enlarged sectional view showing the attachment structure ofthe strut mount to a vehicle body.

FIG. 4 is an enlarged sectional view of the strut mount duringvulcanization forming.

FIG. 5 is a sectional view showing an example of modification ofvulcanization forming shown in FIG. 4.

FIG. 6 is a sectional view of a strut mount according to a secondembodiment.

FIG. 7 is a perspective view of a caulking nut according to the secondembodiment.

FIG. 8 is a sectional view showing the state of the caulking nutsticking fast to the attachment hole.

FIG. 9 is a perspective view showing an example of modification of thecaulking nut.

FIG. 10 is a sectional view showing the state of the caulking nut of themodification example sticking fast to the attachment hole.

FIG. 11 is a sectional view of the strut mount explaining an effect ofthe third embodiment described above.

FIG. 12 is a sectional view of conventional strut mount.

BEST MODE FOR CARRYING OUT THE INVENTION

The strut mount 10 according to the first embodiment of the presentinvention is explained on the basis of FIGS. 1 to 5.

As shown in FIG. 1, the strut mount 10 comprises an inner fitting 12which is fixed by inserting an upper extremity 1 a of a piston rod 1 ofa shock absorber from below, an outer fitting 14 attached to the vehiclebody side, surrounding an outer circumference of the inner fitting 12,and a rubber elastomer 16 in the form of a ring interposed between theinner and outer fittings 12, 14 to unite both in one piece, and isattached to an attachment plate 2 of the vehicle body, curved in theform of upwardly convex sphere. The attachment plate 2 of the vehiclebody has an opening 3, to which the strut mount 10 is assembled frombelow.

The inner fitting 12 is a roughly tubular steel product disposed on theinside of the rubber elastomer 16, and at its outer circumferentialsurface an inner circumferential surface of the rubber elastomer 16 isvulcanization bonded. The inner fitting 12 has a circular fixed surfaceportion 18 square to the rod 1, an opening 20 is provided at the centerof the fixed surface portion 18, and the rod 1 is fixed to the fixedsurface portion 18 by a nut 9 under a condition of being inserted intothe opening 20. The inner fitting 12 comprises a first member 22 in theform of a cup having upward opening with the fixed surface portion 18 asa bottom surface, a second member 24 in the form of a cup havingdownward opening to receive the upper extremity of the rod 1 from below,and the fixed surface portion 18 is formed by jointing both bottomsurfaces of the first and second members 22, 24. The second member 24serves as a seat for a bound bumper.

The outer fitting 14 is a steel product comprised of a cylindricalportion 26 disposed nearly parallel to the inner fitting 12 so as tocover the inner fitting 12 from outside and an attachment piece 28extendedly disposed outwardly in the direction square to the axialdirection from the upper extremity of the cylindrical portion 26, andembedded in the rubber elastomer 16. At the attachment piece 28, theouter fitting 14 is tightened on the underside of the attachment plate 2of the vehicle body by the bolt. For that purpose, the attachment piece28 is curved in the form of a sphere of upwardly convex in correspondingwith a shape of the lower surface of the attachment plate 28.

The attachment piece 28 is provided with a fastening surface portion 30exposed from the rubber elastomer 16 and fastened to the attachmentplate 2 of the vehicle body by the bolt. In this embodiment, thefastening surface portion 30 is provided at three points at acircumferential edge of the outer fitting 14 as shown in FIG. 2. A nut32 screwed by the bolt 4 inserted from the upper side of the attachmentplate 2 of the vehicle body is provided integrally on the fasteningsurface portion 30 by burring working.

As shown in FIGS. 2, 3, a non-fastening surface portion 36 lowered via adifferent level portion 34 is provided so as to surround the fasteningsurface portion 30. The fastening surface portion 36 is formed in theform of a plane with respect to the spherical fastening surface portion30, lower than the fastening surface portion 30 by one step. Therefore,the non-fastening surface portion 36 is disposed oppositely via a slightclearance under a condition where the attachment piece 28 is fixed tothe attachment plate 2 of the vehicle body, with non-contactingcondition with the underneath of the attachment plate 2.

When producing the strut mount 10, the rubber elastomer 16 isvulcanization formed with the first member 22 of the inner fitting 12and the outer fitting 14 set up in a die 40. At this time, as shown inFIG. 4, the fastening surface portion 30 of the attachment piece 28 isin the state of being exposed from the rubber elastomer 16 when beinginterposed between an upper die 42 and a lower die 44. A forcing surfaceportion 46 forcing the non-fastening surface portion 36 is provided forthe upper die 42 disposed on the upper surface side of the attachmentpiece 28. The forcing surface portion 46 is provided so as to be pressedagainst the non-fastening surface portion 36 around the fasteningsurface portion 30, instead of the fastening surface portion 30, whenclosing the dies. The rubber is thus prevented from coming into thefastening surface portion 30 outside of the non-fastening surfaceportion 36 by pressing the forcing surface portion 46 against thenon-fastening surface portion 36.

When attaching the strut mount 10 as described above to the vehiclebody, lift up the strut mount 10 so that the inner fitting 12 insertsthrough the opening 3 of the attachment plate 2 of the vehicle body,align the nut 32 on the fastening surface portion 30 to the underside ofthe bolt hole 5 of the attachment plate 2, and screw the bolt 4,vertically inserted via a washer 6 from above the attachment plate 2through the plate surface, into the nut 32. Thus, the fastening surfaceportion 30 of the outer fitting 12 is fastened to the attachment plate 2of the vehicle body by the bolt to complete attachment of the strutmount.

According to the configuration described above, curving the attachmentpiece 28 of the outer fitting 14 and the attachment plate 2 of thevehicle body in the form of a sphere allows the attachment portion ofthe strut mount 10 to have high rigidity, bringing about good runningproperties.

Since the rubber is prevented from coming into the fastening surfaceportion 30 during vulcanization forming by means of the non-fasteningsurface portion 36, a rubber burr can be avoided from producing at thefastening surface to the vehicle body.

FIG. 5 shows an example of modified forcing surface portion 46 in theaforementioned embodiment. In this example, a sealing protrusion 48 witha sectional shape of roughly triangle is provided, extending along thedifferent level portion 34, for the forcing surface portion 46, andpressed against and cut into the non-fastening surface portion 36. Thesectional shape of the sealing protrusion 48 is not limited to atriangle, and semi-circular and rectangular shape may also be used.

Although irregularities are produced on the surface against which theprotrusion 48 is cut and pressed, it does not have an influence onfastening to the attachment plate 2 of the vehicle body because ofnon-fastening surface portion 36. And, by making the sealing protrusion48 cut into the surface, the rubber coming into the fastening surfaceportion 30 can be blocked more effectively, thus further favorablypreventing the rubber burr on the fastening surface from being produced.

Then, the strut mount 50 according to the second embodiment is explainedon the basis of FIGS. 6 to 10.

The second embodiment differs from the first embodiment in that acaulking nut 52 is provided, instead of the aforementioned nut 32produced by the burring working, as a nut screwed by the bolt 4 thatserves to fasten the outer fitting 14 to the vehicle body. Explanationof the points, to which the same number as the first embodiment isdesignated, is omitted because of the same structure.

As shown in FIG. 6, on the fastening surface portion 30 for theattachment piece 28 of the outer fitting 14, a nut attachment hole 54 isprovided, to which a caulking nut 52 is stuck. As shown in FIGS. 7, 8,the caulking nut 52 comprises a nut portion 56 disposed on the undersideof the attachment piece 28 and a cylindrical portion 58 inserted intothe nut attachment hole 54 from the underside. On the innercircumferential surface of the nut portion 56 and the cylindricalportion 58, screw threads are cut continuously, wherein the bolt 4 isscrewed. The caulking nut 52 is stuck to the nut attachment hole 54, thecircumference of which, on the attachment piece 28, is pressurized andcaulked, which is then diminished in diameter. For the purpose of makingharder than the attachment piece 28, the caulking nut 52 is a hardenedsteel product.

Having larger diameter than the nut attachment hole 54, the nut portion56 gets caught in the circumferential edge of the nut attachment hole 54so as not to slip through and come out of the attachment piece 28upwardly. A groove 60 is made around the cylindrical portion 58 on theupper surface of the nut portion 56, so that the extra wall of theattachment piece 28 cuts into there when pressurizing the circumferenceof the nut attachment hole 54.

The cylindrical portion 58 has an outside diameter enough to be insertedinto the nut attachment hole 54, and its outer circumferential surfaceis corrugated 62 so that the extra wall of the attachment piece 28 cutsinto the cylindrical portion 58 when pressurizing the circumference ofthe nut attachment hole 54. The closer to the base extremity side (lowerside) the cylindrical portion 58 reaches, the deeper the corrugation 62is formed on the outer circumferential surface. The extra wall being cutinto serves to restrain the caulking nut 52 from slipping throughdownward.

The procedure of attaching the strut mount 50 to the attachment plate 2of a vehicle body is described below. First, the cylindrical portion 58of the caulking nut 52 is inserted from below into the nut attachmenthole 54 of the strut mount 50 being assembled, and then thecircumference of the nut attachment hole 54 of the attachment piece 28is pressurized and caulked from above. At this time, the nut attachmenthole 54 is diminished in diameter, and the inner circumferential surfacethereof is stuck fast to the cylindrical portion 58. Further, the extrawall of the attachment piece 28 cuts into the corrugation 62 on theouter circumferential surface of the cylindrical portion 58, wherebyforming a steady rest that restrains the bolt 4 from turning togetherwith the caulking nut 52, with the result to secure a predeterminedturning torque. Being made of hardened steel, the caulking nut 52 willnot be deformed.

With the strut mount lifted up so that the inner fitting 12 passesthrough the opening 3 of the attachment plate 2 of the vehicle body, andalso with the underside of the bolt hole 5 on the attachment plate 2aligned with the bolt hole of the caulking nut 52, provided that thebolt 4 inserted vertically into the plate surface from above theattachment plate 2 through a washer 6 is screwed into the caulking nut52 and the attachment piece 28 of the outer fitting 14 is bolted to theattachment plate 2 of the vehicle body, attachment of the strut mount 50is completed.

According to the configuration described above, since the bolt 4 can beinserted perpendicularly to the plate surface even when the attachmentplate 2 of the vehicle body is curved, it is not necessary to make thebolt hole 5 of the attachment plate 2 larger, and problems such aslooseness can be dissolved. Further, since the attachment piece 28 iscaulked to secure the caulking nut 52, it is not necessary to thickenthe attachment piece 28 of the outer fitting 14 just like in the case ofburring working, so that the weight of the components can be reduced.Besides, because the nut is not welded, post working can easily beperformed even after vulcanization forming of the rubber, capable oflaborsaving during operations and reducing cost.

FIGS. 9 and 10 show examples of modified caulking nuts. This examplerelates to the caulking nut 70 the cylindrical portion of which isupset.

The caulking nut 70 comprises a nut portion 72 disposed on the undersideof the attachment piece 28 and a cylindrical portion 74 that is insertedinto the nut attachment hole 54 from the underside. The caulking nut 70is caulked, upset and secured to the nut attachment hole 54 bypressurizing and upsetting the cylindrical portion 74 outwardly. For thepurpose of making harder than the attachment piece 28, the caulking nut70 is a hardened steel product.

Having larger diameter than the nut attachment hole 54, the nut portion72 gets caught in the circumferential edge of the nut attachment hole 54so as not to slip through and come out of the attachment piece 28upwardly. On the inner circumferential surface of the nut portion 72,screw threads are cut, wherein the bolt 4 is screwed.

The cylindrical portion 74 has an outside diameter enough to insert intothe nut attachment hole 54, and its inside diameter is larger than theI.D. of the nut portion 72 so as not to deform the screw threads of thenut portion 72 when being caulked. Having a chamfering 76 on the aboveside of the circumferential edge of the nut attachment hole 54, theupsetting upper extremity of the cylindrical portion 74 is gotten caughtso as not to slip through and come out of the caulking nut 70downwardly.

INDUSTRIAL APPLICABILITY

According to the strut mount of the present invention, rigidity can beraised without thickening the attachment plate of a vehicle body toimprove vehicle running stability, by curving the attachment piece ofthe outer member and the attachment plate of the vehicle body in theform of a sphere.

Besides, since the non-fastening surface portion is provided by beinglowered via a different level portion around the fastening surfaceportion of the attachment piece of the outer member to the vehicle body,the rubber in a cavity of the forming die is prevented from getting intothe fastening surface, thus keeping the rubber burr from being producedon the fastening surface.

Furthermore, the attachment plate can be curved by the use of thecaulking nut stuck to the underside of the attachment piece of the outermember, without enlarging the bolt hole of the attachment plate of thevehicle body, the weight of the products can also be reduced by thinningthe plate thickness, and cost reduction can be accomplished bylaborsaving during operations.

1. A strut mount comprising an inner member to which an upper extremity of a rod of a buffer is fixed, an outer member attached to a vehicle body while surrounding an outer circumference of the inner member, and a rubber elastomer interposed between the inner and outer members to dampen vibration: wherein the outer member is provided with an attachment piece that is fitted and secured using bolts to an attachment plate of the vehicle body from underneath, wherein the attachment piece comprises (a) bolt-fastening surface regions having a curvature of a partial sphere corresponding to a curved lower surface of the attachment plate, and (b) an upward convex portion inward of the bolt-fastening surface regions, said upward convex portion protruding from the partial sphere toward the attachment plate.
 2. The strut mount as set forth in claim 1, wherein the elastomer is a rubber elastomer stuck to the inner and outer members by means of die forming: wherein the bolt-fastening surface regions are exposed from the rubber elastomer and tightened to the attachment plate of the vehicle by the bolts, and a non-fastening surface portion of plane form is provided around the bolt-fastening surface regions by being lowered via a different level portion.
 3. The strut mount as set forth in claim 2, wherein the rubber elastomer is formed by preventing the rubber elastomer from coming into the bolt-fastening surface regions by pressing a forcing surface portion provided on a forming die against the non-fastening surface portion.
 4. The strut mount as set forth in claim 1, wherein both the attachment piece of the outer member and the attachment plate of the vehicle body are fastened by tightening a bolt screwed to a nut, which is caulked and secured on the lower surface side of the attachment piece of the outer member, from above the attachment plate of the vehicle body.
 5. The strut mount as set forth in claim 4, wherein the nut is a caulking nut with a cylindrical portion that is inserted into a nut attachment hole formed on the attachment piece of the outer member, the caulking nut with the upsetting cylindrical portion being stuck to the attachment piece.
 6. The strut mount as set forth in claim 4, wherein the nut is a caulking nut with a cylindrical portion that is inserted into a nut attachment hole formed on the attachment piece of the outer member, the caulking nut being stuck to the attachment piece by pressurizing the circumference of the nut attachment hole from the direction square to the attachment piece plate surface and diminishing the nut attachment hole in diameter.
 7. The strut mount as set forth in claim 6, wherein the outer circumferential surface of the cylindrical portion of the caulking nut is corrugated, and an extra wall surrounding the nut attachment hole cuts into the corrugated outer circumferential surface of the cylindrical portion as the nut attachment hole is diminished in diameter, the extra wall acting as a steady rest to restrain the caulking nut from turning together with the bolt.
 8. A strut mount comprising: an inner member to which an upper extremity of a rod of a buffer is to be fixed; an outer member surrounding an outer circumference of the inner member, said outer member being provided with an attachment piece fitted and secured to an attachment plate of a vehicle body from underneath, said attachment piece (i) having a lower surface on which nuts are caulked and secured, (ii) comprising (a) bolt-fastening surface regions having a curvature of a partial sphere corresponding to a curved lower surface of the attachment plate and (b) an upward convex portion inward of the bolt-fastening surface regions, said upward convex portion protruding from the partial sphere toward the attachment plate, and (iii) being fastened to the attachment plate of the vehicle body with bolts screwed downward to the nuts through the attachment plate of the vehicle body; and a rubber elastomer interposed between the inner and outer members to dampen vibration and enclosing the outer member, wherein the lower surface of the attachment piece has around each nut the bolt-fastening surface region that is not covered with the rubber elastomer.
 9. A strut mount comprising: an inner member to which an upper extremity of a rod of a buffer is to be fixed; an outer member surrounding an outer circumference of the inner member, said outer member being provided with an attachment piece fitted and secured to an attachment plate of a vehicle body from underneath, said attachment piece (i) having a lower surface on which nuts are attached, (ii) comprising (a) bolt-fastening surface regions having a curvature of a partial sphere corresponding to a curved lower surface of the attachment plate, and (b) an upward convex portion inward of the bolt-fastening surface regions, said upward convex portion protruding from the partial sphere toward the attachment plate, and (iii) being fastened to the attachment plate of the vehicle body with bolts screwed downward to the nuts through the attachment plate of the vehicle body; and a rubber elastomer interposed between the inner and outer members to dampen vibration and enclosing the outer member, wherein the lower surface of the attachment piece has around each nut the bolt-fastening surface region that is not covered with the rubber elastomer.
 10. A strut mount comprising: an inner member to which an upper extremity of a rod of a buffer is to be fixed; an outer member surrounding an outer circumference of the inner member, said outer member being provided with an attachment piece fitted and secured to an attachment plate of a vehicle body from underneath, said attachment piece comprising (a) bolt-fastening surface regions having a curvature of a partial sphere corresponding to a curved lower surface of the attachment plate and (b) an upward convex portion inward of the bolt-fastening surface regions, said upward convex portion protruding from the partial sphere toward the attachment plate, said upward convex portion protruding from the partial sphere toward the attachment plate, wherein both the attachment piece of the outer member and the attachment plate of the vehicle body are fastened with bolts screwed to nuts; and a rubber elastomer interposed between the inner and outer members to dampen vibration and enclosing the outer member, wherein the lower surface of the attachment piece has around each nut the bolt-fastening surface region that is not covered with the rubber elastomer. 